1. Field of the Invention
This invention relates to body support systems, and particularly to those systems designed to support the head and neck during acceleration exposure.
2. Description of the Related Art
During high speed turns and other maneuvers, pilots of modern, high performance aircraft are exposed to high levels of +Gz (head-to-foot) acceleration. While exposed to this "Gz-loading," pilots are unable to voluntarily move their heads. Furthermore, if their heads do not rest against the ejection seat, they are also unable to maintain an upright head position with their eyes also upright and looking forward. The G-force "pushes" their heads towards the cockpit floor resulting in decreased situational awareness, head pain, neck pain and discomfort. Head and neck pain (or even death) from G loading on the unsupported head can also occur during aircraft ejections.
The potential for head and neck injury limits the levels of pilot acceleration exposure. A device to provide head support during acceleration would not only protect pilots but also increase the G levels that can be safely tolerated.
In addition to the need for a head support device during acceleration, there is also a need for head support while wearing a Helmet Mounted Display (HMD). HMDs are being incorporated into a number of current and future aircraft. Because they are mounted on the helmet, HMDs increase the weight of the helmet and thus the weight that head and neck muscles must support. A device to unload the weight of the helmet and HMD from the head and neck muscles would be useful especially during G-loading. Such a support device should be designed so that it does not interfere with head movements or with the attachment of HMD components onto the helmet.
To effectively use an HMD, the head position must be tracked. Modern tracking devices are cumbersome and do not always provide an accurate indication of the position of the head. A device that provides accurate head tracking for all head movements and supports a helmet with an HMD would aid in the full implementation of HMD technology in the cockpit. Finally, head tracking is useful for a number of other applications such as aiming weapons and/or sensors, and conducting biomedical or human factors research.
Currently, there is no device that: 1) provides head support during acceleration and ejection while the subject wears a standard helmet, 2) provides head support during acceleration and ejection while wearing an HMD, and 3) provides an accurate measure of head position.
U.S. Pat. No. 4,923,147 entitled "Head Support/Spine Offloading Ejection Seat Insert" assigned to Rockwell International Corporation, and U.S. Pat. No. 4,664,341 entitled "Head Restraint System" also assigned to Rockwell International Corporation disclose devices for supporting the head during acceleration. Both devices include straps connecting the head support device to the seat or seat-mounted equipment. Because of the helmet-to-seat connection, these straps could get caught on cockpit components and thereby interfere with the normal ejection process. Such an interference would increase the risk of injury to an ejecting pilot.
The '147 patent discloses a head support component which must extend above the top of the helmet to unload the G-forces on the head. This configuration limits the amount of clearance between the head support/helmet combination and the interior of the aircraft canopy. Because of this clearance problem, relatively tall pilots may not be able to fly in cockpits that would be accessible to them if they were not wearing the head support device disclosed in the '147 patent. With the head restraint system disclosed in the '341 patent, downward G loads oriented through the top of the head are not countered by the restraint system and thus must be supported by the pilot's head and neck muscles. As a result, potential injuries due to G loading on the head, especially while the body is in a forward-leaning position, are not prevented.